Remote switching circuit for teleprinter - uses opto-electronic couplers whose transistors, together with transmit and receive units, are located in bridge diagonal

摘要

The remote switching circuit, for a teleprinter, helps establish the connection between exchange and subscriber and consists of semiconductor elements making use of a microprocessor already present at the subscriber end. The local line (al, bl) including the exchange (VST) is located in a rectifier bridge's first diagonal (A - C) and the transmit/receive device of the teleprinter (SK, EM) is located on the bridge's second diagonal (B - D). The second diagonal also contains the phototransistors of two opto electric couplers (K4, K5) and a resistor (R, K3) controlled by an LED.